Double source-build timeout (#38775)

- internal job timed out a couple of times in the last week

.azure/pipelines/ci.yml

@@ -743,6 +743,7 @@ stages:
         container: 'mcr.microsoft.com/dotnet-buildtools/prereqs:centos-7-20210714125435-9b5bbc2'
         buildScript: './eng/build.sh $(_PublishArgs) --no-build-repo-tasks'
         skipPublishValidation: true
+        timeoutInMinutes: 120
 
   # Publish to the BAR and perform source indexing. Wait until everything else is done.
   - ${{ if and(ne(variables['System.TeamProject'], 'public'), notin(variables['Build.Reason'], 'PullRequest')) }}: